1. Field of the Invention
The present invention generally relates to electronic packaging, and more particularly, to a leadless chip carrier design and structure.
2. Description of the Related Art
The microelectronics industry has continued to make significant advances in semiconductor device technology. Semiconductor devices are getting smaller, more dense, and run at higher speeds. However, as device sizes decrease and electrical components are moved closer together, one of the limiting properties of the semiconductor device is the electrical parasitics caused by resistance, capacitance and inductance effects. This is particularly troubling in radio frequency (RF) devices, where it is important to minimize electrical parasitics and to be able to predict their effects reliably. Also, the need to control device generated heat has become more critical as the speeds and power consumption of semiconductor devices has increased.
Controlling electrical parasitics is also important at the packaging level. The structure that supports the semiconductor device (i.e., chip) is commonly referred to as an electronic package. The electronic package is designed to provide electrical interconnection for I/O, signal lines, power supplies, and ground, in addition to environmental and physical protection.
One advantageous form of packaging is the chip carrier which is gaining in popularity. A big reason for this is that chip carriers are very small in size and thus make it possible to fit many devices on a substrate such as a printed circuit board (PCB) or ceramic. The package, as part of the completed semiconductor device, must be low in electrical parasitics and have good thermal dissipation. This is especially important for RF applications.
Electrical parasitics, particularly inductance, are some of the parameters that can adversely affect the performance of electrical packages. Inductance is thus one parameter that should be controlled and reduced. One of the factors contributing to the inductance is the long printed traces found in most packages. Another factor is the lack of a good ground plane located close to the device.
Present packages also have problems with dissipating heat. As semiconductor devices have increased in performance, their power requirements have also increased dramatically. Because of the large amount of power needed to operate a chip, the heat generated by a chip can reach several watts. Dissipation of this heat is an important design consideration of both the chip and chip carrier. Since the chip and chip carrier are made from different materials, each having a different coefficient of thermal expansion, they will react differently to the heat generated by the chip and the outside environment. The resulting thermal stresses can reduce the life of the semiconductor device by causing mechanical failures. Thus, it is desirable to be able to predict accurately the thermal effects of the chip carrier so that the chip carrier can be designed accordingly.
Therefore, there exists a need for a small package for a semiconductor device that would provide low electrical parasitics, predictable heat dissipation along with an efficient ground plane.